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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
753 am CDT Tuesday Apr 21 2015

issued at 747 am CDT Tuesday Apr 21 2015

Updated to include 12z aviation discussion below.


Short term...(today and tonight)
issued at 400 am CDT Tuesday Apr 21 2015

Today and tonight...surface analysis shows a large surface low with a
988mb center over eastern Ontario province this morning with a surface trough
snaking around its periphery from eastern Michigan into northern Illinois and through southern
IA/NE. WV imagery shows a deep 500 mb rotating upper low shifted
slightly westward of the surface feature...allowing the longwave trough to
expand and remain anchored over eastern noam through tonight. These features
will promote isolated/scattered -ra/-sn showers to drift southeastward through the weather forecast office
mpx County warning forecast area for much of the day into tonight...mainly along and north of the
I-94 corridor. Not much in the way of quantitative precipitation forecast but even temperatures
into the middle-upper 30s may be subject to snowflakes due to the deep
cold layer and prominent cold air advection with northwest flow aloft. Highs will range
through the 40s. There will again be the concern for strong winds
over southwestern portions of the County warning forecast area where cloud cover will be less and
can better ably tap into strong winds at the top of the mixing
layer. Have gone with a Wind Advisory for western and southern portion of the
County warning forecast area after collab with surrounding offices. Winds will settle down
to 10 miles per hour or less tonight into tmrw morning. This scenario combined with
decrg clouds and continued cold air advection will allow for temperatures so drop
below the freezing mark early Wednesday morning. Lows tonight will bottom out
in the middle 20s to around 30.

Long term...(wednesday through monday)
issued at 400 am CDT Tuesday Apr 21 2015

The primary weather driver in the long term continues to be the
deeply amplified trough /which is essentially overhead right now/
as it sets up over the northern Great Lakes from Wednesday through
Thursday. During this time...we will be under a persistent
northwest flow aloft...and Canadian high pressure will sink into
the upper Midwest at the surface. So...diurnally driven northwest
winds will persist both days...generally 10 to 20 miles per hour at least
with some gusts over 20...especially on Wednesday. The majority of
the cloud cover associated with the trough will have pushed to the
east of our area...leaving US with abundant sunshine with the
exception of parts of west central WI which may see wrap around
stratus swing through on Wednesday.

Once Friday comes...attention turns to a shortwave ejecting out of
the Colorado Front Range. There is actually decent agreement
between the GFS/ECMWF/Gem in handling this energy...but the
details in how far north the precipitation makes it is where the
difference occur. It looks like as we go through Friday night and
Saturday...a surface low will deepen near Kansas and move nearly
due east. The ec/Gem agree well with this aspect...whereas the GFS
takes the low south through Oklahoma toward Arkansas. Both the
ec/Gem spread moisture and warm air advection lift into southern at least
slight chance probability of precipitation are warranted at this time. However...if the
GFS solution is on the right track...Friday would remain dry.

High pressure looks to build in again on Sunday...before another
shortwave approaches the region Sunday night/Monday...and light
rain will be a possibility.


Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 747 am CDT Tuesday Apr 21 2015

Large deep low pressure center over the central Great Lakes into eastern
Ontario province will keep low VFR/upper MVFR clouds in place for
much of the day. Weak shortwaves rounding the periphery of the
deep low will spread isolated/scattered -ra/-sn showers into mainly the WI
taf sites but possibly kstc/kmsp as well. Conds will improve as
the day progresses and the low shifts off to the east...allowing more
solid VFR ceilings by late this afternoon followed by scattering out of
clouds overnight into Tuesday. Strong/gusty northwest winds will continue
through the day today then diminish to around 10 knots overnight into Tuesday.

Kmsp...VFR ceilings look to prevail although the occasional upper-end
MVFR ceiling cannot be ruled out through this morning...especially if a small
batch of precipitation makes it into kmsp. Otherwise...conds will
gradually improve this evening through overnight...with clouds
scattering out overnight. Strong gusty northwest winds will generally
remain from 290-320 during this taf period. No visibility restrictions
expected as any heavier batches of precipitation look to remain east of

/Outlook for kmsp/
Wednesday...VFR. Winds northwest 15g25kts.
Thursday...VFR. Winds northwest 10-15kt.
Friday...VFR. Winds NE 5-10 knots.


Mpx watches/warnings/advisories...
Minnesota...Wind Advisory from noon today to 6 PM CDT this evening for



short term...jpc
long term...speed

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